class_docstr: The class generates a dictionary for recognition. It pre-defines four
  special tokens: ``start_token``, ``end_token``, ``pad_token``, and
  ``unknown_token``, which will be sequentially placed at the end of the
  dictionary when their corresponding flags are True.
  
  Args:
      dict_file (str): The path of Character dict file which a single
          character must occupies a line.
      with_start (bool): The flag to control whether to include the start
          token. Defaults to False.
      with_end (bool): The flag to control whether to include the end token.
          Defaults to False.
      same_start_end (bool): The flag to control whether the start token and
          end token are the same. It only works when both ``with_start`` and
          ``with_end`` are True. Defaults to False.
      with_padding (bool):The padding token may represent more than a
          padding. It can also represent tokens like the blank token in CTC
          or the background token in SegOCR. Defaults to False.
      with_unknown (bool): The flag to control whether to include the
          unknown token. Defaults to False.
      start_token (str): The start token as a string. Defaults to '<BOS>'.
      end_token (str): The end token as a string. Defaults to '<EOS>'.
      start_end_token (str): The start/end token as a string. if start and
          end is the same. Defaults to '<BOS/EOS>'.
      padding_token (str): The padding token as a string.
          Defaults to '<PAD>'.
      unknown_token (str, optional): The unknown token as a string. If it's
          set to None and ``with_unknown`` is True, the unknown token will be
          skipped when converting string to index. Defaults to '<UKN>'.
docstr: int: Number of output classes. Special tokens are counted.
          
docstr_tok: ["int",":","Number","of","output","classes",".","Special","tokens","are","counted","."]
code: def num_classes(self) -> int:
      """int: Number of output classes. Special tokens are counted."""
      return len(self._dict)
  
file_path: mmocr/mmocr/models/common/dictionary/dictionary.py
imports: from typing import List, Sequence
  from mmocr.registry import TASK_UTILS
  from mmocr.utils import list_from_file
label_desc: Use image node_id 2 for calling the Dictionary obj's underlying member method code with example usage: obj.num_classes() and returns: len